Signature

A cryptographic signature is a mathematical mechanism that allows someone to prove ownership. In the case of Bitcoin, a Bitcoin wallet and its private key(s) are linked by some mathematical magic. When your Bitcoin software signs a transaction with the appropriate private key, the whole network can see that the signature matches the bitcoins being spent. However, there is no way for the world to guess your private key to steal your hard-earned bitcoins.

A hash of a document encrypted with a private key . When the digital signature is attached to the document, then anyone with the public key can create their own hash of that document, decrypt the original hash using the public key, and compare. If the hashes match, then it can be concluded that the document sender is confirmed and the document has not been altered. Otherwise the decrypted hash would not match the generated hash.

A digital digest produced by hashing private and public keys together to prove that a Bitcoin transaction came from a particular address. A cryptographic signature is a mathematical mechanism that allows someone to prove ownership. Bitcoin uses ECDSA for signing transactions. Every transaction must provide a signature matching a public key defined in the previous transaction. In this way only the true owner of a secret private key associated with a given public key can access the bitcoins.